Chain drives are used both in human driven vehicles such as bicycles and in motor driven systems such as motorcycles, conveyer belts and other motor driven systems. Different approaches for measuring the force exerted on a chain are described. European patent EP 0380553 discloses a device for measuring tensile forces at any desired location along a chain. The device comprises a load pick-up body which has a chain-link engaging member on each end thereof and which is intended to pick-up the tensile load between the chain-link engaging members, and further comprises a means for measuring and indicating the tensile load picked-up by the body. U.S. Pat. No. 5,207,108 discloses a transducer for sensing tension loading of a conveyor chain, including a transducer link having opposite ends for connection along the chain and also including a transducer member mounted by the transducer link between its ends. The transducer member includes an opening and at least one strain gauge mounted thereon. A clamp of the transducer compresses the transducer member as tension loading is applied between the opposite ends of the transducer link to provide a strain gauge indication of the extent of the tension loading. EP 1907810 discloses transmission chain comprising a data collection device mounted on at least one of the links. A strain gauge sensor is mounted on the inwardly facing surface of an outer link plate symmetrically about a center link thereof and measures the strain on the link plate.
There is a variety of devices available today for measuring the force exerted by a bicyclist. They measure the force as applied to different components of the bicycle such as distortion to the bicycle frame. In EP 1324913 the level of a force or torque (T) exerted by a rider on the pedals of a bicycle is calculated by a signal-processing device on the basis of a measurement signal which is obtained from a sensor which is attached to the frame of the bicycle in order to measure the deformation which occurs in the frame. In U.S. Pat. No. 8,327,723 the measuring device is intended to measure forces on a bicycle pedal mounted to rotate on a pedal spindle fixed at the free end of a crank-set crank-arm. The device includes force sensors positioned on the pedal spindle and able to detect the force directed perpendicularly to the pedal spindle and to supply a signal dependent on the force detected, and electronic elements able to process the signals received from the sensors.
U.S. Pat. No. 7,878,946 discloses an exercise bicycle including a flywheel, a drive train coupled to the flywheel, and pedals coupled to the drive train. A user of the exercise bicycle expends power by exerting force on the pedals to spin the flywheel. The exercise bicycle further includes a power meter. The power meter includes a friction pad comprising a flywheel contact surface in contact with the flywheel and a temperature sensor located within the friction pad. The temperature sensor measures the temperature of the flywheel contact surface. The power meter further includes an output meter coupled to the temperature sensor, the output meter converting a temperature change of the flywheel contact surface as measured by the temperature sensor into a calculated power expended by the user. U.S. Pat. No. 6,356,848 discloses measuring the speed and tension of the drive chain and calculating the power output therefrom. The apparatus of the invention includes a chain speed sensor, a chain tension sensor, and electronic processing apparatus to calculate and display the power output based upon the chain measurements. Patent application US 20120261895 discloses two or more sensors placed on the chainstay of the bicycle to measure the vibrational frequency of the chain. Such vibration data can be used to determine the tension of the chain, and may also further compute the power transmitted by the chain, in conjunction with the measurement of chain speed. The invention provides a method and apparatus for conditioning and filtering the signals from the vibration sensors, as well as an arrangement for positioning the sensors on the bicycle.